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Low-Profile Metasurface Antenna for Broadband RCS Reduction and Omnidirectional Radiation

by Liqiu Hu, Sijia Li, Kefeng Ji, Yuhao Wu and Zhiyun Zhang

Materials 2026, 19(12), 2542; https://doi.org/10.3390/ma19122542 - 12 Jun 2026

Cited by 2 | Viewed by 418

Abstract

A low-profile, low radar cross-section (RCS) omnidirectional metasurface antenna is investigated and proposed in this letter. The antenna consists of a top circular patch, a three-layer dielectric substrate, a full metal ground, a multi-layer polarization conversion metasurface, and four short vias for connecting [...] Read more.

A low-profile, low radar cross-section (RCS) omnidirectional metasurface antenna is investigated and proposed in this letter. The antenna consists of a top circular patch, a three-layer dielectric substrate, a full metal ground, a multi-layer polarization conversion metasurface, and four short vias for connecting the top patch to the ground. Wideband impedance matching is achieved by modifying an F-shaped feeding structure. The broadband RCS reduction is realized by loading the antenna with the polarization conversion metasurface (PCM) in an appropriate array configuration. The antenna prototype has been fabricated and measured in an anechoic chamber. Experimental results illuminated that the antenna features a low profile of 0.051λ₀ (λ₀ is the wavelength at 2.35 GHz) and a 10 dB impedance bandwidth of 2.11–2.62 GHz (a fractional bandwidth of 21.56%). Significantly broadband RCS reduction is achieved from 7.05 to 16.96 GHz, with a maximum reduction of –28 dB and an average reduction of –12.51 dB. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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15 pages, 20470 KB

Open AccessArticle

Design of Novel Fe-Doped NiCo-LDH/NiFeCo-Oxide Composite Nanosheets Grown on Carbon Fiber Cloth for High-Performance Flexible Asymmetric Supercapacitor

by Wenyi Qiu, Zuo Zhu, Xiaoming Li, Hongwei Luo, Junfeng Chen, Chen Wang and Linchi Zou

Materials 2026, 19(9), 1747; https://doi.org/10.3390/ma19091747 - 24 Apr 2026

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Abstract

Layered double hydroxides (LDH) demonstrate significant potential in flexible superca-pacitors due to their high energy storage capability and adjustable architectures. Never-theless, the practical specific capacitance exhibited by current LDH remains below expec-tations, which is attributed to suboptimal electrode performance and limited active sites. [...] Read more.

Layered double hydroxides (LDH) demonstrate significant potential in flexible superca-pacitors due to their high energy storage capability and adjustable architectures. Never-theless, the practical specific capacitance exhibited by current LDH remains below expec-tations, which is attributed to suboptimal electrode performance and limited active sites. Herein, a novel Fe-doped NiFeCo-LDH/NiFeCoO nanosheet composite supported on car-bon cloth was designed and fabricated as a flexible electrode. In this composite, the Ni-FeCo-LDH supplies numerous reactive centers and accelerates electrochemical kinetics, while the NiFeCoO and carbon cloth significantly improve electrical conductivity and cy-cling stability. Moreover, the heterointerface formed between the LDH and the metal oxide phase further facilitates charge transfer. Owing to such synergistic interactions, the pre-pared NiFeCo-LDH/NiFeCoO@CC electrode demonstrates an excellent areal specific ca-pacitance of 3.282 F cm⁻² at a current density of 1 mA cm⁻², while maintaining a high ca-pacity preservation reaching 88.09% following 5000 cycles. Furthermore, the assembled NiFeCo-LDH/NiFeCoO@CC//AC asymmetric supercapacitor delivers an outstanding en-ergy density reaching 0.302 mWh cm⁻² under a power density of 0.776 mW cm⁻², coupled with an excellent capacitance preservation of 85.29% over 5000 cycles. Meanwhile, it can maintain its initial capacitance under varying bending degrees, rendering it widely ap-plicable for future advanced flexible and wearable electronic devices. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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14 pages, 7130 KB

Open AccessArticle

The Ta Seed-Buffer Layer Microstructure and Its Influence on the Magnetic and Structural Parameters of CoFeB/MgO Layers

by Jarosław Kanak, Monika Cecot, Witold Skowroński, Antoni Żywczak, Marta Gajewska, Jerzy Wrona, Wiesław Powroźnik and Maciej Czapkiewicz

Materials 2025, 18(24), 5558; https://doi.org/10.3390/ma18245558 - 11 Dec 2025

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Abstract

In this paper, we discuss the structural and magnetic properties of Ta(d)/Co₄₀Fe₄₀B₂₀/MgO/Ta multilayers. The CoFeB wedge layer was deposited on three buffers differing in Ta layer thickness: d = 5, 10, and 15 nm. A [...] Read more.

In this paper, we discuss the structural and magnetic properties of Ta(d)/Co₄₀Fe₄₀B₂₀/MgO/Ta multilayers. The CoFeB wedge layer was deposited on three buffers differing in Ta layer thickness: d = 5, 10, and 15 nm. A structural analysis showed that the Ta seed-buffer of 5 nm was amorphous, whereas thicker Ta grew in a β-tetragonal disordered structure. X-ray reflectivity measurements revealed that the Ta/CoFeB interface roughness for annealed samples ranged from 0.55 to 0.67 nm for a sample with a 0.85 nm CoFeB layer and decreased to approximately 0.47 nm for thicker CoFeB layers, while the average interface CoFeB/MgO thickness was about 0.2–0.3 nm. The morphological roughness of the amorphous single 5 nm Ta layer was the lowest, whereas crystalline grains in thicker Ta buffers induced higher roughness. The 5 nm thick MgO layer exhibited a strong (001)-oriented texture, which was the highest for the smoothest 5 nm Ta buffer. The magnetic dead layer thickness for the annealed sample with a 15 nm Ta buffer was 0.39 nm and increased with the decrease in the Ta buffer thickness. Temperature-dependent measurements offered further insight into the diffusion processes and the formation of the magnetic dead layer (MDL) at the Ta/CoFeB interface. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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19 pages, 4484 KB

Open AccessArticle

Near-Compensated Ferrimagnetism in Disordered Co_0.5Mn_1.5Al Half-Heusler Alloy: Experimental and Theoretical Studies

by Emese Bender, Răzvan Hirian, Cristian Leoştean, Roman Atanasov, Radu George Haţegan, Lucian Barbu-Tudoran and Diana Benea

Materials 2025, 18(19), 4449; https://doi.org/10.3390/ma18194449 - 23 Sep 2025

Cited by 1 | Viewed by 1209

Abstract

This study investigates the electronic, magnetic, and transport properties of the Co_0.5Mn_1.5Al half-Heusler alloy, a promising candidate for spintronic applications due to its potential half-metallic and ferrimagnetic characteristics. Experimental efforts focus on structural characterization using X-ray diffraction to examine [...] Read more.

This study investigates the electronic, magnetic, and transport properties of the Co_0.5Mn_1.5Al half-Heusler alloy, a promising candidate for spintronic applications due to its potential half-metallic and ferrimagnetic characteristics. Experimental efforts focus on structural characterization using X-ray diffraction to examine substitutional disorder, such as Co/Mn site migration and Mn/Al site mixing, and their impacts on magnetic and transport properties. Magnetic characterization, including magnetization and susceptibility, reveals an N-type ferrimagnetic behaviour with a Curie temperature of 670 K. Transport experiments probe resistance and magnetoresistance across various temperatures and magnetic fields to uncover conduction mechanisms and spin-dependent effects. Theoretical band structure calculations, utilizing the Korringa–Kohn–Rostoker Green’s function method, investigate the electronic structure and the role of disorder in shaping magnetic and transport properties. This integrated experimental and theoretical approach aims to clarify the alloy’s suitability for applications in exchange bias or antiferromagnetic spintronics. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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17 pages, 2892 KB

Open AccessArticle

Stoichiometry of Bulk Nb_1−βSn_β Superconductors Synthesised by Arc Melting

by Mahboobeh Shahbazi, Henrietta E. Cathey, Ali Dehghan Manshadi, Jose Alarco and Ian D. R. Mackinnon

Materials 2025, 18(13), 3050; https://doi.org/10.3390/ma18133050 - 27 Jun 2025

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Abstract

We present an alternative process for production of binary Nb_1−βSn_β superconducting phases using pre- and post-treatment of arc-melted Nb + Sn ingots. This process combines sequential sintering, arc melting, and annealing procedures that provide dense, bulk samples of Nb_1−β [...] Read more.

We present an alternative process for production of binary Nb_1−βSn_β superconducting phases using pre- and post-treatment of arc-melted Nb + Sn ingots. This process combines sequential sintering, arc melting, and annealing procedures that provide dense, bulk samples of Nb_1−βSn_β with varying stoichiometry between 0.18 < β < 0.25 depending on annealing time and temperature. We show, through magnetization measurements of these Nb_1−βSn_β bulks, that annealing of arc-melted samples at 900 °C for 3 h significantly enhances J_c values compared with arc-melted Nb_1−βSn_β samples without annealing. Microstructural analyses show that optimum grain size and orientation are achieved by sintering and annealing at lower temperatures (i.e., 720 °C and 900 °C, respectively) with short annealing times (i.e., <10 h). Processing at higher temperatures and for longer times enhances grain growth and results in fewer pinning centres. The optimum process creates effective pinning centres that deliver a J_c = 6.16 × 10⁴ A/cm² at 10 K (and ~0.2 T), compared with J_c = 3.4 × 10⁴ A/cm² for Nb_1−βSn_β subjected to a longer annealing time at a higher temperature and J_c = 775 A/cm² for an arc-melted sample without post-annealing. We suggest that further work addressing post-treatment annealing times between 3 h < t_post < 60 h at temperatures between 900 °C and 1000 °C will provide the opportunity to control stoichiometric and microstructural imperfections in bulk Nb_1−βSn_β materials. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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14 pages, 3776 KB

Open AccessArticle

Magnetocaloric Properties and Microstructures of HoB₂ and Nb-Substituted HoB₂

by Mahboobeh Shahbazi, Ali Dehghan Manshadi, Kiran Shinde and Ian D. R. Mackinnon

Materials 2025, 18(4), 866; https://doi.org/10.3390/ma18040866 - 17 Feb 2025

Cited by 2 | Viewed by 1579

Abstract

We report on the arc melt syntheses of HoB₂ and Nb-substituted HoB₂ polycrystalline ingots and their magnetocaloric and microstructural properties. XRD data and microstructural analysis reveal that a nominal 10% Nb addition during synthesis results in changes to unit cell parameters [...] Read more.

We report on the arc melt syntheses of HoB₂ and Nb-substituted HoB₂ polycrystalline ingots and their magnetocaloric and microstructural properties. XRD data and microstructural analysis reveal that a nominal 10% Nb addition during synthesis results in changes to unit cell parameters and grain morphology. Interpretation of the refined cell parameters using Vegard’s law shows that Nb substitutes into HoB₂ with stoichiometry Ho_0.93Nb_0.07B₂. Arc-melted products are polycrystalline bulk samples containing minor phases such as Ho₂O₃, Ho, and HoB₄. Nb substitution results in a smaller grain size (~sub-micron) and a higher Curie temperature, T_C, compared to HoB₂. With a 10 T applied field, the maximum magnetic entropy, ΔS_M, for HoB₂ and for Ho_0.93Nb_0.07B₂, is 46.8 Jkg⁻¹K⁻¹ and 38.2 Jkg⁻¹K⁻¹ at 18 K and 21 K, respectively. Both samples show second-order phase transitions. Despite high totals of minor phases (e.g., ~10 wt.% and ~25 wt.%), the calculated relative cooling powers are greater than 1300 Jkg⁻¹ and 600 Jkg⁻¹ at 10 T and 5 T, respectively. The magnetocaloric properties of both samples are consistent with Holmium boride compounds prepared via alternative methods. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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14 pages, 4706 KB

Open AccessArticle

Valley-Related Multipiezo Effect in Altermagnet Monolayer V₂STeO

by Yufang Chang, Yanzhao Wu, Li Deng, Xiang Yin and Xianmin Zhang

Materials 2025, 18(3), 527; https://doi.org/10.3390/ma18030527 - 24 Jan 2025

Cited by 11 | Viewed by 2313

Abstract

The multipiezo effect realizes the coupling of strain with magnetism and electricity, which provides a new way of designing multifunctional devices. In this study, monolayer V₂STeO is demonstrated to be an altermagnet semiconductor with a direct band gap of 0.41 eV. [...] Read more.

The multipiezo effect realizes the coupling of strain with magnetism and electricity, which provides a new way of designing multifunctional devices. In this study, monolayer V₂STeO is demonstrated to be an altermagnet semiconductor with a direct band gap of 0.41 eV. The spin splittings of monolayer V₂STeO are as high as 1114 and 1257 meV at the valence and conduction bands, respectively. Moreover, a pair of energy degeneracy valleys appears at X and Y points in the first Brillouin zone. The valley polarization and reversion can be achieved by applying uniaxial strains along different directions, indicating a piezovalley effect. In addition, a net magnetization coupled with uniaxial strain and hole doping can be induced in monolayer V₂STeO, presenting the piezomagnetic feature. Furthermore, due to the Janus structure, the inversion symmetry of monolayer V₂STeO is naturally broken, resulting in the piezoelectric property. The integration of the altermagnet, piezovalley, piezomagnetic, and piezoelectric properties make monolayer V₂STeO a promising candidate for multifunctional spintronic and valleytronic devices. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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Review

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28 pages, 597 KB

Open AccessReview

Ab Initio Calculations of Spin Waves: A Review of Theoretical Approaches and Applications

by Michael Neugum and Arno Schindlmayr

Materials 2025, 18(18), 4431; https://doi.org/10.3390/ma18184431 - 22 Sep 2025

Viewed by 1447

Abstract

Spin waves represent an important class of low-energy excitations in magnetic solids, which influence the thermodynamic properties and play a major role in technical applications, such as spintronics or magnetic data storage. Despite the enormous advances of ab initio simulations in materials science, [...] Read more.

Spin waves represent an important class of low-energy excitations in magnetic solids, which influence the thermodynamic properties and play a major role in technical applications, such as spintronics or magnetic data storage. Despite the enormous advances of ab initio simulations in materials science, quantitative calculations of spin-wave spectra still pose a significant challenge, because the collective nature of the spin dynamics requires an accurate treatment of the Coulomb interaction between the electrons. As a consequence, simple lattice models like the Heisenberg Hamiltonian are still widespread in practical investigations, but modern techniques like time-dependent density-functional theory or many-body perturbation theory also open a route to material-specific spin-wave calculations from first principles. Although both are in principle exact, actual implementations necessarily employ approximations for electronic exchange and correlation as well as additional numerical simplifications. In this review, we recapitulate the theoretical foundations of ab initio spin-wave calculations and analyze the common approximations that underlie present implementations. In addition, we survey the available results for spin-wave dispersions of various magnetic materials and compare the performance of different computational approaches. In this way, we provide an overview of the present state of the art and identify directions for further developments. Full article

(This article belongs to the Special Issue Recent Advances in Magnetic and Electronic Materials and Their Applications)

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